Multi-functional self-healing composites

ABSTRACT: Structural fiber-reinforced composites can experience subcritical damage in the form of delamination, matrix cracking, or fiber breaks well before final failure. During the Phase I research we will improve a proven self-healing polymer matrix via the addition of carbon nanotubes (CNTs). The remendable polymer utilizes thermally reversible Diels Alder cycloaddition reactions to repair broken bonds. Addition of CNTs into this healable polymer matrix will improve the mechanical properties of the composites and also increase the thermal and electrical conductivity, both of which will aid in the remending process. Damage and healing is detected by applying an addressable conducting network that will both sense resistance changes due to damage in the composites as well as deliver current for resistive heating to addressable locations within the composite for repair. BENEFIT: The proposed technology provides a solution to the serious problem of repairing impact, delamination and microcracking damage in aircraft and vehicles. Currently, such damage is difficult to repair, especially in situations where the carbon fiber structure is remotely deployed. The proposed CNT composite material will have improved mechanical, electrical, and thermal properties. Additionally, once damage is detected, a simple and low cost method of thermally repairing the structure can be performed that requires only an elevated temperature to remend Diels Alder bonds within the polymer matrix. This method of healing has advantages over other strategies such as the localized release of a chemical reagent in that repeated damage to the same location can be repaired.